1. Technical Field
The present invention relates to a tunable interference filter, an optical filter module, and a photometric analyzer.
2. Related Art
A known tunable interference filter extracts light having a specific wavelength from light having plural wavelengths.
For example, JP-A-2003-14641 discloses a tunable interference filter having a fixed mirror and a movable mirror provided with a variable gap therebetween for selectively transmitting light having a specific wavelength (hereinafter, such a filter may be referred to as an “etalon”).
In a tunable interference filter having the structure of JP-A-2003-14641, when the gap dimension between the fixed mirror and the movable mirror is changed, the movable mirror moves and maintains the gap dimension. As the movable mirror deflects, the movable mirror pushes the air in the space forming the gap. If the channel in which the air is pushed is long or narrow, there have been problems that air resistance (drag by the air) acts in the direction in which the movable mirror moves and the time it takes for the movable mirror to move increases. Accordingly, it takes a longer time to obtain transmission light having a desired wavelength due to the movement of the movable mirror, and the responsiveness of the tunable interference filter is lowered.